12 Essential LED Outdoor Lighting Terminology You Must Know

When purchasing outdoor lighting, there are key terminologies that are essential to understand.

This article compiles 12 major terminologies related to outdoor lighting and provides a detailed introduction to these terms.

It also highlights the issue of some unscrupulous vendors who falsely label these key parameters. We emphasize the false markings in this article as well.

What is the IP Rating?


For outdoor lighting, waterproofing is an important specification.

The IP (Ingress Protection) rating is an international standard used to measure the protective capabilities of electronic equipment, such as lighting fixtures and appliances, against dust and water.

The IP rating is typically composed of two digits: the first digit indicates the level of protection against solid objects, and the second digit indicates the level of protection against liquids.

First Digit after IP: Dust Protection Level

NumberProtection RangeDescription
0No protectionNo special protection against external elements
1Prevents entry of solids larger than 50mm in diameterPrevents accidental contact with internal parts by human body parts like the hand, and prevents entry of large objects larger than 50mm in diameter
2Prevents entry of solids larger than 12.5mm in diameterPrevents contact with internal parts by fingers, and prevents entry of medium-sized objects larger than 12.5mm in diameter
3Prevents entry of solids larger than 2.5mm in diameterPrevents entry and contact with internal parts by tools, wires, and similar small objects larger than 2.5mm in diameter or thickness
4Prevents entry of solids larger than 1.0mm in diameterPrevents entry and contact with internal parts by tools, wires, and similar small objects larger than 1.0mm in diameter or thickness
5Dust protectedCompletely prevents entry of solid objects, although not fully dust-tight, the quantity of dust entering will not affect normal operation of the device
6Dust tightCompletely prevents entry of solid objects and dust

Second Digit after IP: Water Protection Level

NumberProtection RangeDescription
0No protectionNo special protection against water or moisture
1Protection against dripping waterDripping water (such as condensation) will not damage the device
2Protection against dripping water when tilted up to 15 degreesDripping water will not damage the device when it is tilted from its normal position up to 15 degrees
3Protection against sprayed waterProtection against rain or water sprayed from any angle up to 60 degrees from the vertical will not damage the device
4Protection against splashing waterWater splashing against the enclosure from any direction will not cause harmful effects
5Protection against water jetsProtection against low-pressure water jets for at least 3 minutes
6Protection against powerful water jetsProtection against heavy seas or powerful jets of water for at least 3 minutes
7Protection against immersionProtection in water up to 1 meter deep for 30 minutes
8Protection against submersionProtection against continuous immersion in water beyond 1 meter. The exact conditions are specified by the manufacturer for each device.

For many outdoor lighting fixtures, a protection level of IP65 is already sufficient, such as street lights and floodlights. However, some outdoor lighting requires IP66 or IP67 ratings, like fixtures installed on the ground, including wall washers, in-ground lights, and tree lights, etc.

It’s important to be aware that some dishonest vendors might falsely label IP ratings. Moreover, many outdoor lights fail to meet their waterproofing standards in actual use, leading to premature failure. This is often because these vendors use substandard, cheaper casings to reduce costs.

Luminous Flux (lm)

Luminous flux, measured in lumens (lm), is a photometric quantity derived from radiation’s effect on a standard photometric observer. It represents the brightness of a light source more directly than just the power (wattage) of the light.

Light Efficiency (lm/w)

Simply put, light efficiency is the lumens produced per watt of power consumed. Modern outdoor lighting fixtures typically have an efficiency of 110-150 lm/W. It’s essential to distinguish between LED chip efficiency and the overall efficiency of the LED fixture.

LED Chip Efficiency & LED LAMP Efficiency

LED chip efficiency can reach between 180 lm/W and 220 lm/W. However, the efficiency of LED fixtures is often lower because about 10% of lumens are lost due to the fixture’s casing and lens, and another 10% may be lost due to the power supply.

Beware of false claims about fixture efficiency. A reliable way to verify claims is to ask for the IES document, which is a highly credible file generated by testing machines.

LED chip efficiency still has potential for improvement, although there is a theoretical limit to LED efficiency. For more on the limit of LED chip efficiency, see the limit light effect of LED.

Illuminance (LUX)

Illuminance is the luminous flux per unit area, measured in lux (lx), where 1 lx = 1 lm/m². It’s a simple concept: divide the light flux by the area it needs to illuminate.

Average Illuminance

This is the total luminous flux required for a space divided by the total area of that space.

Light Distribution

Light Distribution Diagram

This represents the intensity of light from a source or fixture in different directions in space, often shown in curves or tables, also known as distribution photometry. IES files include light distribution graphs.

Uniformity of Illuminance

This is the ratio of the minimum to the average illuminance on a specified surface, denoted as U0. Many outdoor spaces have specific requirements for U0, such as road lighting and stadium lighting standards. For detailed outdoor lighting standards, you can refer to the most comprehensive road lighting standards in 2023 and 2024 comprehensive guide to stadium lighting.

Maintenance Factor

LED chips experience lumen depreciation over time, meaning their light output gradually diminishes. With LED chips now having a lifespan of up to 65,000 hours (over ten years), lighting designs must account for this depreciation to ensure that illuminance standards are met years down the line.

Glare Value


The International Commission on Illumination (CIE) uses this parameter to quantify the subjective discomfort caused by outdoor lighting fixtures, such as those used in stadiums, to the human eye. Solutions to mitigate glare are discussed in the 2024 comprehensive guide to stadium lighting.

What is the Color Rendering Index?

The Color Rendering Index (CRI) can be understood as the degree to which a light source accurately reveals the true colors of objects. CRI is denoted by Ra, with a minimum value of 1 and a maximum of 100. Sunlight has a Ra of 100, and although artificial light cannot achieve the color rendering of sunlight, it can come infinitely close. Therefore, the higher the CRI, the better.

A light source with a higher Ra will display colors that are closer to the “true colors” of the objects it illuminates. Additionally, there is generally an inverse relationship between CRI and light efficiency; light sources with a high CRI usually have lower light efficiency.

For outdoor lighting fixtures, a CRI of RA > 70 is usually sufficient. As an outdoor lighting manufacturer (ADN Solar Street Light), we can also produce outdoor fixtures with a CRI of RA >80, should your lighting project require it.

What Harm Does a Low CRI Cause?


A low CRI can impact the eye’s ability to recognize colors accurately, preventing objects from displaying their true colors. If this persists, it can lead to a decline in color discrimination ability, resulting in serious vision problems and eye diseases, such as color blindness and weakness in students. Prolonged exposure to poorly color-rendering light sources can also reduce the sensitivity of the eye’s cone cells. The brain has to concentrate more, either consciously or unconsciously, when identifying objects, leading to eye fatigue and potentially causing myopia.

What is Color Temperature?


Color temperature measures the color components in light. Taking sunlight as an example, the color temperature is higher during the day and lower at night. Generally, the color temperature for road lighting and outdoor public lighting ranges between 3000K-6000K. Many landscape lights are typically set to a color temperature of 1700K-2300K (yellow light).

What is Beam Angle?

The beam angle refers to the angle between where the light intensity falls to 1/10th of its maximum. Common beam angles for light fixtures include 5°, 10°, 15°, 20°, 25°, 30°, 45°, 60°, 90°, and 120°.

The light distribution of street lights (ADN Solar Street Light) resembles the shape of bat wings, typically featuring a beam angle of 70° X 140°.

Bat wing for road lighting

Different LED lenses can achieve these various beam angles and light distributions.

Input Voltage

Most outdoor lighting fixtures are connected directly to grid power, so their input voltage is typically 100V-275V AC. However, many landscape lights, for safety and ease of installation, utilize a 24V DC input voltage.

Call to Action

ADNLITE, with over a decade of experience in manufacturing industrial lights, landscape lights, and solar lights, boasts a factory that has produced more than 100 varieties of outdoor lighting fixtures. These products cater to a wide range of outdoor industrial lighting projects, outdoor landscape lighting projects, and outdoor public lighting projects. We welcome everyone to contact ADNLITE for the customized production of your outdoor lighting solutions.